In indirect aqueous printing, an aqueous ink is jetted onto an intermediate imaging surface, referred to herein as a transfix surface member. The ink is partially dried on the transfix surface member prior to transfixing the image to a print medium, such as a sheet of paper.
It is desirable for the transfix surface member to provide both wet image quality, including desired spreading and coalescing of the wet ink; and the image transfer of the dried ink. Wet image quality is best achieved when the transfix surface member has a high surface energy that causes the aqueous ink to spread and wet the surface. The second challenge—image transfer—is best achieved when the transfix surface member has a low surface energy so that the ink, once partially dried, has minimal attraction to the surface and can be more easily transferred to the print medium.
A sacrificial wet layer is sometimes applied to the transfix surface member to aid in providing the desired wet image quality and image transfer. In cases where a sacrificial wet layer is employed, transfix surface members having both sufficiently high surface energy for good wettability and spreading of the sacrificial layer on the transfix member surface, and sufficiently low surface energy to provide release of the sacrificial layer, are desired. In addition, the transfix member can be exposed to relatively high temperatures during printing, so that a thermally stable surface material for the transfix member is also desirable.
Surface coatings exhibiting moderate wettability (not as difficult to wet as silicone or fluorinated materials, yet still exhibit the desired non-stick or anti-contaminant properties) could provide the desired surface energy for transfix surface members. Coatings with moderate wettability could enable spreading of an ink or stabilization of a sacrificial wet layer. However, materials which exhibit both high thermal stability and moderate wettability are virtually non-existent.